The lifting of the wheels of vehicles, and more generally the movement thereof not during travel, is an activity which is troublesome, laborious and potentially risky to the health and the safety of the operators owing to the weight, which at times is also substantial, of the vehicle wheels. In repair garages, bodyshops and at tyre repair workshops, there are used balancing machines, tyre changing machines and other auxiliary technical machines for the vehicle, which provide for the lifting of the vehicle wheels to a given height, and the positioning thereof on supports which are provided for the purpose on the machines. In order to fulfil those objectives, there have been developed apparatuses which allow lifting, and more generally movement, of vehicle wheels including wheels of considerable weight, reducing the effort of the operator with a series of safeguards with respect to the safety of the operation. Those apparatuses also allow centering of the vehicle wheel on a support, for example, of a balancing machine.
An example of a lifting apparatus is described in US 2013/0277632. It comprises a support plane for a vehicle wheel which can be lifted and lowered as a result of a scissor type articulation which has creeping trucks and which is controlled by a pneumatic piston type actuator, whose shaft is provided at the end thereof with a bearing which presses the scissor type articulation in accordance with, at the same time, a cam-like profile so as to reduce the lifting force for the operator. Such a lifting apparatus requires a compressed air supply source. It is also rather complex and readily subjected to wear owing to the creeping trucks of the scissor type articulation and the pressure mechanism with the bearing which follows the cam-like profile. It is further not very flexible in terms of operation, because the pressure parameters are predetermined and can be modified only with difficulty by the operator, who can act only on the air pressure in the piston type actuator, but cannot modify the cylinder capacity, nor the profile of the cam.
Another example of a known lifting apparatus is described in U.S. Pat. No. 8,205,494, wherein it is connected to a balancing machine for vehicle wheels. This lifting apparatus also comprises a support plane for a vehicle wheel which can be lifted and lowered as a result of a scissor type articulation which has creeping trucks. A processing unit provides for control of the lifting action of the vehicle wheel up to a height at which the hub thereof is aligned with the support shaft of the balancing machine. The reaching of the exact height is established by a sensor which is placed on the balancing machine and which operates in accordance with two different methods depending on where it is positioned. According to a first configuration, the sensor is positioned at the same height as the support shaft of the balancing machine, and reads, transversely relative to the plane of the vehicle wheel, the distance of the tread band of the tyre. When that distance is at a minimum, the hub of the wheel is at the same height as the support shaft of the balancing machine, and in that position the stopping of the lifting apparatus is brought about. In the alternative, the sensor is placed on a wheel protection screen, in the vertical of the support shaft. The sensor initially reads the distance between the base, on which the wheel is supported, and the tip of the tyre thereof, so as to calculate the diameter of the wheel, and the position of the hub. While the wheel is lifted, the sensor reads the distance from the tread band and brings about the stopping of the lifting action when the hub has reached the height of the support shaft. Such a lifting apparatus is also readily subjected to wear as a result of the creeping trucks of the scissor type articulation. Furthermore, the lifting and lowering operations are slow and they require continuous processing of the data from the sensor. An error of the sensor during measurement of the height of the wheel or the distance from the tread band thereof may compromise the correct alignment of the wheel on the support shaft of the balancing machine, with a further resultant loss of time. Furthermore, the operator is at risk of forgetting the lifting apparatus in the lifted position after having clamped the wheel on the support shaft, with the high risk of starting the balancing machine without having lowered the lifting apparatus.
Therefore, an object of the present invention is to overcome the disadvantages of the prior art and to improve the features thereof, providing a lifting apparatus which allows an operator to lift, and generally move, a vehicle wheel with a minimum of effort. Another object of the invention is to provide a lifting apparatus which is simple and economical but which is highly reliable and safe to use. Another object of the invention is to provide a lifting apparatus which can be connected to a balancing machine which allows operation with safety and speed for balancing vehicle wheels, and in particular for balancing a plurality of identical vehicle wheels.